#include "bits/stdc++.h"
using namespace std;
#define rep(i,n) for(int i=0;i<n;i++)
#define REP(i,x,n) for(int i=x;i<n;i++)
#define ALL(v) (v).begin(),(v).end()
#define MP(a,b) make_pair(a,b)
typedef long long LL;
typedef pair<int, int> PI;
typedef vector<int> VI;
const LL MOD = 1000000007LL;
LL L[200000];
int main() {
	int N;
	cin >> N;
	rep(i, N) cin >> L[i];
	LL K;
	cin >> K;
	double l = 0, r = 1e10;
	rep(i, 100) {
		double m = (l + r) / 2;
		LL sum = 0;
		rep(j, N) {
			sum += (LL)floor(L[j] / m);
		}
		if (sum >= K) l = m; else r = m;
	}
	printf("%.15lf\n", l);
}